The development of the Internet has led to an increasing demand for high-speed broadband access. In the case of larger commercial and government organizations, the requirement for high-speed broadband access has been obtained through the use of various technologies including private lines (for example T1 lines), private networks and satellite links. These types of technologies, however, are neither economically nor technically feasible for residential homes and small businesses.
A large unfulfilled demand remains for a high-speed broadband internet access in the area of residential homes and small business. This segment of the commercial market also has the greatest potential for growth in the future, and the development of this market is also critical to the development of electronic commerce. The ultimate success of many potential commercial Internet applications including, for example, on demand movies, video conferencing, real-time online gaming, online shopping, etc. depends on the expansion of high-speed broadband access on a large scale into the average residential home and small business.
While new technologies have been developed that would permit the extension of broadband capability into the residential home and small business environment, they are limited in practical application. Cable television companies, for example, have recently introduced cable modem technology that permits broadband access using coaxial cable lines. Many communities, however, still lack basic cable service let alone broadband cable access. High speed broadband access via a satellite link is also now possible for residential homes and small business, but such systems generally only provide broadband capability on the downlink side. In other words, downlink from the satellite to the end user is a broadband connection, but the uplink from the end user to the internet service provider is usually provided over conventional telephone lines using conventional modems. The inability for such systems to provide bi-directional broadband makes them useless for applications such as real-time video conferencing.
The one network that is already coupled to almost every home and small business is the Public Switched Telephone Network (PSTN). The PSTN, however, was originally developed using copper technology that was never intended to provide the broadband capability now in demand. Traditional plain old telephone service (sometimes referred to as POTS) connects to a home or small business using a twisted pair of copper wires originally designed to carry voice information in the form of an analog signal. In order to enable digital data transfer between computers over the POTS, a modem has conventionally be used at the transmission end to convert digital data from the transmitting computer to an analog signal that can be switched over the POTS, and at the receiving end converts the analog signal back into digital data. Data transmission rates with conventional dial-up modems, however, are limited to about 56 Kbps (thousands of bits per second).
Accordingly, attempts have been made to provide technology that can upgrade and expand the capability of the conventional PSTN to increase data transfer rates above those possible with conventional dial-up modem services. One technology that has been developed to provide broadband capability to homes and small businesses is Digital Subscriber Line (DSL). In fact, there are a number of different versions of DSL, and the designation “xDSL” is sometimes utilized to generalize the different versions of DSL such as ADSL, HDSL and RADSL. Regardless of the specific version, DSL basically depends upon advanced digital signal processing methods to transfer as much data as possible through a conventional twisted copper pair of the PSTN. Downstream data transfer rates as high as 8 Mbps (megabits per second) are possible with some versions of DSL.
While DSL is a great improvement over conventional dial-up modems, the technology has a number of limitations. One of the more significant limitations is the maximum transmission range of DSL. Depending on the gauge of wire used, the end user must be located no more than just 5.5 km (using 24 gauge wire) from a central office of the telephone company. Further, in practice, line attenuation increases with line length. Thus, utilization of the maximum range of 5.5 km causes a corresponding drop in data transfer rates to just around 1.5–2.0 Mbps. While it may be possible to extend the range of DSL, such an extension would require a large capital investment to install optical fiber communication lines between the central office of the PSTN and DSL subscribers. Accordingly, a wholesale reconstruction of the PSTN would be required.
Moreover, the DSL architecture does nothing to improve the overall capacity of the PSTN. In a DSL system, data received from an end user is separated in a serving central office of the PSTN into conventional voice data and multimedia data. The conventional voice data is transmitted through the PSTN using synchronous transmission in a conventional manner. The multimedia data is transmitted over a separate line from the conventional voice data also through the use of a synchronous transmission protocol. The DSL architecture does nothing to increase the bandwidth capability of the existing copper or optical transmission lines. Accordingly, the implementation of DSL causes a corresponding drop in the number of conventional voice communications that can be handled by the PSTN.
Still further, the DSL architecture requires a number of different data transfer protocols to be utilized. For example, a computer at a user's location is normally connected to a DSL modem. Communication between the modem and the computer is normally accomplished using a Local Area Network (LAN) protocol such as Ethernet. A DSL protocol is then utilized to communication between the DSL modem and the serving central office of the PSTN. A separate synchronous transmission protocol is then utilized within the PSTN for data transfer. Finally, a further optical transmission protocol is utilized if optical transmission lines are provided within the PSTN. Accordingly, the resulting architecture requires a large number of protocol layers resulting in latency in the network and complexity in the overall system.
As will be readily appreciated from the disadvantages described above, it would be desirable to provide a high-speed broadband capability between the PSTN and an end user over a conventional copper twisted pair without the range limitations of DSL.
It would also be desirable to provide a high-speed broadband public switched network that utilized a single protocol from a broadband service provider, through the inter-office facilities, through the serving central office and to the end user, thereby providing a substantially “flat” network and reducing latency problems associated with protocol conversions.
Still further, it would also be desirable to provide the above features while expanding the capacity of the PSTN without requiring a change in infrastructure, thereby allowing a public switched broadband network to be implemented using conventional copper and optical fiber transmission lines.